1. Field of the Invention
The present invention relates to a vehicle tire, in particular while not exclusively, for cars and light trucks, provided with a high wear-resistance tread.
The invention also relates to said tread, as well as to a vulcanizable rubber composition of the type comprising a cross-linkable unsaturated chain polymeric base, and to a sulfur-based vulcanizing system.
In the following description and in the subsequent claims, the terms: cross-linkable unsaturated chain polymeric base, are used to indicate any non cross-linked polymer or polymer blend, either natural or synthetic, capable of assuming all the physical-chemical and mechanical characteristics typical of elastomers as a result of cross-linking (vulcanization) with sulfur-based systems.
2. Description of the Related Art
In the field of vehicle tire manufacturing, one of the more difficult objects to be reached has always been that of increasing the wear resistance of the tire, achieving at the same time a satisfactory skid resistance on wet road.
The difficulties for achieving the aforementioned object have been worsened in recent times by the need of satisfying at the same time also a third parameter, namely, a reduced rolling resistance, which is at present strongly required by the tire market, which further complicates the problem of achieving a satisfactory compromise between all of the aforementioned parameters.
Generally, a low rolling resistance is achieved by using in the rubber composition of the tread the so-called light reinforcing fillers (first of all silica) , a lower amount of carbon black, a suitable amount of carbon black having a reduced surface area and being, as such, less reinforcing, or a combination of two or more of the aforementioned measures.
Among the formulation criteria for the rubber compositions of the treads usually adopted in the art in order to increase the wear resistance of the tire, it is possible to mention the use of polybutadiene in the polymeric base of the rubber composition or the use of more reinforcing fillers and/or greater amounts of the same.
However, in both cases, a worsening in other properties of the tire, such as wet skid resistance in the first case, and rolling resistance in the second case, is observed.
In order to increase the wear resistance of the tire tread to be used in heavy vehicles, it was also proposed to introduce specific thermosetting resins in the polymeric base, such as for instance m-cresol-formaldehyde or phenol resins, as is described in Japanese patent applications JP 7-109381, JP7-109382 and JP7-109383.
However, in so doing, a greater rigidity of the tread at low temperature, and a higher energy dissipation due to hysteresis with a possible increase in rolling resistance were observed.